I just got home from a shopping trip for a car power adapter for my 770.

Best price I found (out of the TWO places that had adapters with the right tips) was at Target for $9 in their Automotive isle they have a adapter for all Nokia phones.

I also picked up a 1 socket to 3 socket cig lighter adapter and a cassette adapter that I think should work to provide me with audio.

PS Dont let the cellphone store monkeys mess with your 770, I nearly had a disaster when one grabbed it, stuck a generic power adapter in the HEADPHONE jack and tried to power it up.